An anger-prone person, for example, would blow a minor slight or inconvenience out of proportion and want to punish the offender severely.

I was puzzled, however, by this question: why didn’t the patients in analytic therapy report these thoughts spontaneously—especially since they were conscientious in expressing whatever came to mind, no matter how embarrassing? Hadn’t they been aware of these thoughts in their everyday lives? I came to the conclusion that these thoughts were different from the kind that people generally report to other people.

The violence of humans against humans appalls us but continues to take its toll today. The dazzling technological advances of our era are paralleled by a reversion to the savagery of the Dark Ages: unimaginable horrors of war and wanton annihilation of ethnic, religious, and political groups. We have succeeded in conquering many deadly diseases, yet we have witnessed the horrors of thousands of murdered people floating down the rivers of Rwanda, innocent civilians driven from their homes and massacred in Kosovo, and blood flowing in the killing fields of Cambodia. Wherever we look, east or west,...